Design And Research Of The Detection System For The Microwave Power Sensors

A novel detection system for the MEMS microwave power sensors is designed in this paper.Firstly, the definition and application fields of microwave power sensors are introduced, and the basic principle of the traditional microwave power sensors is studied. The amplifying circuit and the filter circuit in the microwave power sensor system are introduced, respectively. The main research work is also introduced.And then, a one-dimensional sensitivity analytical model of the MEMS microwave power sensor is established based on the thermal-electric conversion principle and the Fourier heat steady equation. The relationship of the parameters and the sensitivity is discussed. And then, combining with the characteristics of MEMS microwave power sensors, the Fourier heat equation for the different district is expressed based on the refinement partition to improve the usefulness of the model. On this basis, the approximate analytical model of MEMS microwave power sensor is obtained. Finally, the system-level model is derived to research MEMS microwave power sensor,and the model includes the relationship among the output voltage with the power and the frequency.Then microwave power sensor is measured with the microwave probe test platform. The output voltage is obtained with the power and the frequency. With the frequency at 8GHz, 10 GHz, 12 GHz,the sensitivity are 0.231 m V/m W, 0.220 m V/m W and 0.215 m V/m W, respectively. With the power at50 m W and 100 m W, the output voltage decreases with the frequency, which provides a favorable theoretical basis for the system integration.Next,the detection system for a weak signal is designed. This system can be performed with high accurate amplification, and low noise filter. The detection system consists of two parts, the amplifier and the filter circuit. The amplification circuit chooses the high precision, controllable gain AD8221 chip as the core. The filtering circuit adopts the second-order voltage-controlled low-pass filter circuit. The amplifier circuit, the filter circuit and the detection system are simulated with PSpice. The gain of the detection system is 750(with a 100? adjustable resistance), and the bandwidth is 80 HZ. Then the MC simulation of the detection system is finished. The purpose is to research the DC characteristics and AC characteristics of the detection system with an adjustable resistor RG analysis within the random variation range of 10%.Finally, the detection system of the microwave power sensor is fabricated and measured. The measured data and the theoretical data are compared. When RG is 80??90??100??110?, themeasured gain of the detection system is 782?751?742?715, respectively. while the theoretical values is 790?760?750?720, respectively. Therefore, the detection system can effectively detect the output signal of MEMS microwave power sensor. By adjusting the resistance RG, the gain of the detection system can be changed, and thereby the output signal can be chosen more freedom.Finally, the contents of text are summarized, and some innovations and the improvement for the further research in this study are proposed.